1. Field of the Invention
The present invention relates to a method of manufacturing an organic electroluminescence (EL) display device.
2. Description of the Related Art
An organic EL element that is a component of an organic EL display device includes a first electrode formed as a lower electrode, a stacked structure (organic compound layer) which is made of an organic compound and includes at least an emission layer, and a second electrode formed as an upper electrode, which are stacked on a substrate in the stated order. In this case, the emission layer forming the organic EL element is formed into a desired pattern by using, for example, an evaporation method performed via a shadow mask, a selective coating method by ink jetting, or a photolithography method. Of those methods, when the photolithography method is used, in order to protect the emission layer against a solution containing a photoresist, an intermediate layer is formed between a resist layer and the emission layer. Note that, after the resist layer is patterned, the intermediate layer is subjected to dry etching together with the organic emission layer to be processed (partially removed).
By the way, when the photolithography method is used, the emission layer is irradiated with ultraviolet rays when the photoresist is patterned, and is irradiated with plasma light when the intermediate layer and the emission layer are subjected to dry etching. At this time, short-wavelength light contained in the ultraviolet rays and the plasma light may cause reactions such as degradation and recombination of materials forming the emission layer, which may cause damage such as structure change of the emission layer. When the emission layer is damaged by the ultraviolet light and the plasma light, luminous efficiency of the organic EL element may be lowered and the durability thereof may be deteriorated.
Therefore, various proposals have been conventionally made for protection of the emission layer against ultraviolet light and plasma light. For example, in Japanese Patent No. 4507759, there is proposed a method in which, in a case where the emission layer is patterned by a photolithography method, the intermediate layer is formed so as to contain a light absorbing material so that the light absorbing material absorbs the ultraviolet light and the plasma light.
By the way, in Japanese Patent No. 4507759, as a specific constituent material for the intermediate layer, a water-soluble polymer is employed. However, an inorganic pigment that is the light absorbing material to be added to the intermediate layer made of a water-soluble polymer is made of a metal oxide, a salt of metal, or the like, and has a property of being resistant to etching with an O2 gas. Therefore, the inorganic pigment to be added as the light absorbing material has an etching rate smaller than that of the water-soluble polymer to be subjected to etching with the O2 gas, and hence the inorganic pigment is difficult to be subjected to collective etching with the water-soluble polymer. As a result, the inorganic pigment remains as a residue when the dry etching with the O2 gas is performed, which may cause a short-circuit between the first electrode and the second electrode. Thus, display failure occurs in some cases.